Buprenorphine, a partially synthetic opiate, has been contemplated for prolonged analgesia via transdermal formulations. Buprenorphine transdermal delivery systems are of particular interest because buprenorphine is a potent, partial agonist opioid analgesic with desirable therapeutic properties. For example, buprenorphine is 50 to 100 times more potent than morphine, but has a much safer therapeutic index than morphine (see Wallenstein S L, et al., Crossover Trials in Clinical Analgesic Assays: Studies of Buprenorphine and Morphine, Pharmacotherapy, G(5): 225–235, 1986). Further, the partial agonist properties of buprenorphine are useful in the treatment of opioid addiction.
There are several types of transdermal formulations of buprenorphine reported in the literature. See, for example, U.S. Pat. No. 5,240,711 (Hille et al.), U.S. Pat. No. 5,225,199 (Hidaka et al.), U.S. Pat. No. 5,069,909 (Sharma et al.), U.S. Pat. No. 4,806,341 (Chien et al.), and U.S. Pat. No. 5,026,556 (Drust et al).
The transdermal delivery of buprenorphine presents challenges to the pharmaceutical formulator as up to 70% or more buprenorphine is left in the patch after use due to the fact that buprenorphine exhibits poor skin penetration. This presents problems with formulating the dosage form and ensuring that a non-variable dosage is delivered as prescribed. Also, the large amount of residual buprenorphine remaining in the patch after use can be subject to abuse and diversion.
There exists a need in the art for a transdermal application of a compound which has the benefits of buprenorphine while minimizing the associated formulation, dosing and abuse problems discussed above.